* We need a directory walker that can handle symlinks, empty directories,
and some other odd needs. This commit contains a directory walker that
can do all that. The walker returns information about the files in the
directories that we can then use to implement different strategies for
copying the files to the remote machines.
* Add local_follow parameter to copy that follows local symlinks (follow
is for remote symlinks)
* Refactor the copying of files out of run into its own method
* Add new integration tests for copy
Fixes#24949Fixes#21513
